Today in the U.S. national airspace system (NAS), air traffic controllers make use of paper flight strips in controlling aircraft under their jurisdiction. Within an air traffic control tower, strips are physically passed between tower controllers with different roles (clearance delivery, ground control, local control) with each controller storing the strips in ordered strip bays and making markings on the strips to record interactions with pilots. Strips are also transferred between the control tower and the terminal radar room, in some cases by gravity down drop tubes, in other cases by a strip bar code scan that triggers reprinting of the strip in the radar room. This system can be inefficient and the paper flight strips can be lost, mislabeled by a controller, or inadvertently destroyed.